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Old 13th Nov 2017, 2:37 pm   #7
Hermit6345
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Join Date: Oct 2006
Location: North Wiltshire, UK.
Posts: 617
Default Re: BEME Mini Loop - silent

Have you measured the volts on G2 of the DK91? I think that they normally use G1 as the oscillator grid, with a 47k or similar to deck and G2 as the oscillator anode. The HT rail is fed via a resistor and tickler coil to G2 and a tuned coupling coil feeds back to G1 so the whole thing then oscillates.The feed resistor is usually decoupled to ground so check the potential on the DK side of that resistor. Be wary of the dreaded McMurdo B7G valve holder. The metal bits inside the socket break and although you see a voltage on the soldered part of the socket, it doesn't get to the valve pin. I expect you will have checked these things anyway. A signal at IF fed to the DK91 signal grid should appear at the LS so that would check the IF and back end stages. I expect that you will have fed a signal generator as a substitute LO at LO+IF into G1 of the DK91? I suspect that the radio you have is a bit more sophisticated than a simple battery portable and you will have done all the logical tests anyway.

Ian
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